为什么我在检查数据库中的值时总是得到“FALSE”？

Question

我想检查数据库中是否存在该值，但是当我运行下面的代码时，我总是得到错误。 谁能帮帮我吗？？

$key_in = $key_in_error = "";

if ($_SERVER["REQUEST_METHOD"] == "POST") {

    if (empty(trim($_POST["key_in"]))) {
        $key_in_error = "Please enter job number.";
    }
//    } else {
//        $key_in = trim($_POST["key_in"]);

        $key_in = mysqli_real_escape_string($link,$key_in);  // SECURITY!
        $result = mysqli_query($link,"SELECT * FROM files WHERE job_no='$key_in'");
        if (mysqli_fetch_row($result)) {
            header("location: downloads.php");
        } else {

            echo"Not valid job number!";
        }
    }

Answer 1

尝试这个

$key_in = $key_in_error = "";

if ($_SERVER["REQUEST_METHOD"] == "POST") {

    if (empty(trim($_POST["key_in"]))) {
    $key_in_error = "Please enter job number.";}
//    } else {
//        $key_in = trim($_POST["key_in"]);

        $key_in = mysqli_real_escape_string($link,$key_in);  // SECURITY!
        $result = mysqli_query($link,"SELECT * FROM files WHERE job_no='$key_in'");
        if (mysqli_num_rows($result)>0) {
            header("location: downloads.php");
        } else {

            echo"Not valid job number!";
        }
    }